Process for fabricating a color cathode ray tube screen structure having superimposed optical filter means therein

ABSTRACT

A process is provided for fabricating a multi-windowed screen structure for a color cathode ray tube effecting enhanced absorption of ambient light and providing contrast improvement of the image display. The process comprises the superposed deposition of primary, secondary, and tertiary layers of diversely-hued subtractive primary colorants in the form of heat formable optical filter materials, pairs of which are evidenced as dual-layered filter components disposed in respective windows of the structure. The deposition of each layer of filter material involves the usage of a photosensitive protective coating that by selective exposure controls the deposition of the overlaid filter materials and effects definitive photo-formation of the window areas. The protective coating comprises a negative photosensitive resist material admixed with an inert substance that is thermally and chemically inactive to the temperatures and materials encountered in the screening process. Since the discretely positioned windows associated with the respective filter layers are formed in accordance with the shaping of the apertures in a spatially related pattern mask, each of the dual-layered filter windows exhibits a uniformly shaped periphery free of indentations, being so defined by a uniform opaque interstitial encompassment homogeneously made up of the three distinct layers of superposed filter materials. Disposed over the dual-layered filter windows in the screen structure is a compatible pattern of cathodeluminescent phosphor elements, which produce color emissions that are colorimetrically related to the respective superposed filter elements in the windows therebeneath.

United States Patet 1 Gallaro et a1.

[ PROCESS FOR FABRICATING A COLOR CATHODE RAY TUBE SCREEN STRUCTURE HAVING SUPERIMPOSED OPTICAL FILTER MEANS THEREIN [75] Inventors: Anthony V. Gallaro, Auburn;

Robert A. Hedler, Seneca Falls, both of N.Y.

[73] Assignee: GTE Sylvania Incorporated,

Stamford, Conn.

[22] Filed: Nov. 2, 1973 [21] Appl. No.: 412,144

[52] US. Cl. 96/30; 96/1; 96/l.2; 96/36.1;96/36.2; 96/383; 96/351;

Primary Examiner-William R. Trenor Attorney, Agent, or FirmNorman J. OMalley; Frederick H. Rinn; Cyril A. Krenzer [57] ABSTRACT A process is provided for fabricating a multiwindowed screen structure for a color cathode ray tube effecting enhanced absorption of ambient light and providing contrast improvement of the image display. The process comprises the superposed deposition of primary, secondary, and tertiary layers of diversely-hued subtractive primary colorants in the form of heat formable optical filter materials, pairs of which are evidenced as dual-layered filter components disposed in respective windows of the structure. The deposition of each layer of filter material involves the usage of a photosensitive protective coating that by selective exposure controls the deposition of the overlaid filter materials and effects definitive photoformation of the window areas. The protective coating comprises a negative photosensitive resist material admixed with an inert substance that is thermally and chemically inactive to the temperatures and materials encountered in the screening process. Since the discretely positioned windows associated with the respective filter layers are formed in accordance with the shaping of the apertures in a spatially related pattern mask, each of the dual-layered filter windows exhibits a uniformly shaped periphery free of indentations, being so defined by a uniform opaque interstitial encompassment homogeneously made up of the three distinct layers of superposed filter materials. Disposed over the dual-layered filter windows in the screen structure is a compatible pattern of cathodeluminescent phosphor elements, which produce color emissions that are colorimetrically related to the respective superposed filter elements in the windows therebeneath.

4 Claims, 11 Drawing Figures I PROCESS FOR FABRICATING A COLOR CATI-IODE RAY TUBE SCREEN STRUCTURE HAVING SUPERIMPOSEI) OPTICAL FILTER MEANS THEREIN CROSS-REFERENCES TO RELATED APPLICATIONS This application contains matter disclosed but not claimed in three related US. Pat. applications filed concurrently herewith and assigned to the assignee of the present invention. These related applications are Ser. Nos. 412,143, 412,142, and 412,145.

BACKGROUND OF THE INVENTION This invention relates to color cathode ray tubes and more particularly to a process for fabricating a color cathode ray tube screen structure providing improved purity and contrast of the color image display.

Cathode ray tubes, particularly those of the type employed in color television applications for presenting multi-colored display imagery, conventionally utilize patterned screens that are comprised of repetitive groups of related color-emitting phosphor materials. Such groupings are normally disposed relative to the interior surface of the tube viewing panel as bars, stripes, or dots depending upon the type of cathode ray tube structure under consideration. For example, in the well-known shadow mask color tube construction, the screen pattern is conventionally composed of a great multitude of repetitive tri-color emissive areas formed of selected cathodoluminescent phosphors, which, upon predetermined electron beam excitation, produce additive primary hues to provide the desired color imagery. Spatially related to the screen is a foraminous structure or patterned mask member having a vast number of discretely formed apertures therein. Each of these apertures in the patterned member is related to a specific tri-component grouping of related coloremitting phosphor areas of the screen pattern, in a spaced manner therefrom to enable the selected electron beams traversing the apertures to impinge the proper areas of the phosphor screen therebeneath.

With the advancement of the color television art, there has been a continued desire to improve the contrast ratio of the color screen display, whereof several approaches have been proposed. One such proposal .to improve contrast concerns the absorbing of ambient light by the utilization of a neutral density filter member, formed ofa tinted cover plate, superposed over the viewing panel of the tube. Since neutral density filters are not appreciably selective in the visible band of the color spectrum, the intended absorptive efficiency cannot be fully realized in eliminating the reflective ambient light falling within the spectrum bandpass ofthe display emission. Another approach to improve the contrast ratio of a color image display is the utilization of a tinted faceplate or viewing panel per se. Tinting or coloring of the glass comprising the faceplate attenuates the light transmission of that member, thereby reducing the evidenced brightness of the phosphor emissions emanating from the electron excited screen. In addition, there are absorptive shortcomings similar to those of the aforementioned neutral density filter.

Another proposal for improving the contrast of the color screen image, particularly in the dot-type patterned screen, has been the development of a composite screen construction wherein the dot defining interstitial spacing between the respective coloremitting dots of the screen pattern is formed of an opaque lightabsorbing material. In essence, each phosphor dot is enclosed or defined by a substantially dark encompassment which collectively comprise a foraminous pattern in the form of a windowed webbing having an array of substantially opaque connected interstices. While this black surround feature reduces the reflected ambient light in the non-fluorescing areas of the screen, it does not reduce the ambient light reflected from those panel areas associated with the phosphor dot and thelight emission emanating therefrom, which areas evidence a high degree of reflectivity.

An additional proposal for enhancing contrast of the color screen display has been the use of optical filter elements disposed relative to the respective coloremitting phosphors comprising the screen pattern. Both single and plural-layered optical filters have been proposed, each utilizing circular filter elements having large oversize diameters, dimensioned so that their outer peripheral portions overlap in a non-uniform manner to produce an irregularly shaped or indented filter area surrounded by a non-uniform interstitial webbing. In the single layer filter embodiment, the variations in the filter and dot-surround webbing effect a variable absorbency of the ambient light thereby detracting from the complete achievement of the intended contrast enhancement. In both the single and plural layered embodiments, the indented peripheral shaping of the filter windows reduces the areal expanse of the evidenced light output of the screen.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention to reduce the aforementioned disadvantages and to provide a process for fabricating an improved screen structure for a color cathode ray tube evidencing improved display contrast.

.It is another object to provide a process for fabricating an improved color cathode ray tube screen structure incorporating windows having a plurality of optical filmulti-window color screen structure disposed on the inner surface of a cathode ray tube viewing panel. The window areas define discrete dual-layered optical filter elements, each being surrounded by a uniform opaque interstitial encompassment that exhibits peripherally defined smoothness free of indentations, such window shapings being similar to the shape of the apertures in a spatially related pattern mask member. The initial step in the screen fabrication process of the invention comprises coating the interior of the panel with a uniform layer of a negative photosensitive resist material which is admixed with an inert protective substance. The coated panel is then exposed by directing actinic radiation. emanating from a first exposure position, through the apertures in the pattern mask to lightpolymerize those portions of the photosensitive coating mixture in the areas of the screen subsequently occupied by the first filter pattern windows. After a development step which removes the unexposed photosensitive coating mixture, the panel is overcoated with a uniform primary layer of a heat formable first optical filter material and heated to thermally degrade the polymerized window elements formed of the resist material, and to adhere a substantially continuous and transparent primary layer of the first optical filter material to the surface of the panel. The panel is then treated to remove the loosely retained heat degraded materials therefrom, whereupon the primary layer of the first optical filter material evidences a plurality first pattern open filter windows therein. The panel is again coated with a uniform layer of the mixture of the photoresist material and the inert protective substance, and again light exposed to actinic radiation emanating from a second exposure portion to light-polymerize portions of the photosensitive coating mixture in those areas eventually occupied by the second filter pattern windows. Development again removes the unexposed portions of the photosensitive mixture. The panel is next overcoated with a uniform secondary layer of a heat formable second optical filter material, and heated to thermally degrade the polymerized window elements formed of the resist mixture and to adhere a substantially continuous and transparent secondary layer of the second optical filter material to portions of the primary filter layer. Upon removal of the loosely retained degraded materials associated with the exposed areas of the secondary layer, the secondary filter layer has second pattern open filter windows therein. The panel is coated for the third time with a uniform layer of the mixture of photoresist and the inert protective material, then lightexposed from a third exposure position to polymerize portions of the photosensitive coating mixture in those areas subsequently occupied by the third filter pattern windows, afterwards the unexposed portions of the coating mixture are removed by development. Uponuniform application of the tertiary layer of a heat formable third optical filter material, the panel is heated to thermally degrade the respective polymerized window elements formed therein and to provide adherence of a substantially continuous and transparent tertiary layer of a third optical filter material to portions of the second filter layer. The panel is then treated to remove the areas of degraded loosely retained materials therefrom, to provide a tertiary filter layer having third pattern open filter windows therein through which areas of the secondary filterlayer superposed on the primary filter layer are evidenced. Areas of the tertiary filter layer superposed on the primary filter layer are evidenced and defined by the second filter pattern windows; whileareas of the tertiary filter layer superposed on the secondary filter layer are defined by the first filter pattern windows. The first, second, and third duallayered filter pattern areas are associated in the completed screen with specific coloremitting phosphor elements to provide enhanced selective optical filtering for the respective light emitting areas. The combination of the three superimposed discretely patterned filter layers provides a substantially opaque uniformly structured interstitial webbing fully surrounding each of the respective optical filter windows in the screen structure whereof the uniform peripheral encompassment of each filter window is free of indentations.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. la through 1c are cross-sectional views illuscal filter material;

FIGS. 1d through lfare cross-sectional views relating to the deposition of the secondary layer of a second optical filter material;

FIGS. lg through 1i are sectional views illustrating the deposition of tertiary layer of the third optical filter material;

FIG. lj is a sectional view showing the completed screen structure; and

FIG. 2 is a plan view of the completed screen structure taken along the line 2-2 of FIG. lj.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a beter understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following specification and appended claims in connection with aforedescribed drawings.

The multi-windowed color cathode ray tube structure resultingfrom the process described herein, will be delineated as exhibiting substantially round filter window areas therein surrounded by a substantially uniform opaque interstitial encompassment; each of the window areas has a defined peripheral smoothness free of indentations. Other window configurations such as elongated and ovate shapings, are intended to be in keeping with the breadth of this disclosure, such configurations being similar to the shape of the related apertures in a spacially associated pattern mask member. The screen structure so described may be utilized in either post deflection or shadow mask types of color cathode ray tube constructions.

The multi-element filter window screen structure 11 resultant of the process of the invention, as illustrated in FIGS. lj and 2 is of the type, for example. as that used in a conventional shadow mask type of color caathode ray tube. As is well known, conventional tubes of this type employ several electron beams which are directed to converge at a multi-apertured shadow mask, not shown, and thence pass through the apertures therein to impinge selected areas of the composite screen structure spaced therebeneath. The window areas of the screen structure of the invention are comprised of dual-layers of optical filters selected from the subtractive primary color components of cyan, magenta and yellow which are complements of the visually additive red, green and blue primary color components; cyan being equivalent to minus red, magenta to minus green, and yellow to minus blue. Thus, improved optical filtering selectively is achieved and enhanced color purity of the observed display imagery is promoted by disposing a dual-layer of cyan and yellow in the screen structure window areas associated with the green-emitting phosphors, cyan and magenta with the blue-emitting areas, and magenta and yellow with the red-emitting areas. The dual-layer filtering components light attenuation of the glass per se being inherent to the elemental composition thereof. Adhered to the interior surface of this panel is a substantially continuous and substantially transparent primary layer of a first heat formable optical filter material. In this embodiment, the primary layer has substantially round first pattern open window areas 31 formed therein, each window being free of peripheral indentations. By way of example, the hue of this primary layer 21 is a subtractive color, such as cyan, and is of a first organometallic luster composition as will be more fully explained subsequently in this specification. Superposed on this primary filter layer 25 is a substantially continuous and substantially transparent secondary layer of a second heat formable optical filter material of another subtractive primary color differing in hue from that of the primary layer, as for example, a yellow coloration resultant of another of second organo-metallic luster composition. This secondary layer 35 overlays the primary layer 25 and fills in the first of the window pattern areas 31 formed therein. Additionally, the secondary layer 35 has a second pattern of open window areas 41. A substantially continuous and a substantially transparent tertiary layer of a third heat formable optical filter material of still another subtractive primary color of a hue differing from that of the primary and secondary layers, as for example magenta, and is formed of a third organo-metallic luster material. This tertiary layer is superposed over the secondary layer 35 and fills in the second window pattern areas 41 therein, effecting superposition upon a defined area of the underlying primary layer 25 to provide the dual-layer of defined second filter elements 39 in the screen structure 11. The pattern definition of the tertiary layer 45 provides an open third window pattern 51, that defines superposed areas in the secondary and primary filter layers 35 and 25 respectively, thereby delineating the dual-layer of the defined third filter elements 49 in the screen structure. In addition, a portion of the tertiary layer superpositionally covers the secondary filter material disposed in the first pattern window areas 31 of the primary layer to provide the dual-layer first filter element 29. In this instance, the first filter elements are comprised of superposed layers of the subtractive color primaries magenta and yellow, the second filter elements 39 of magenta and cyan, and the third filter elements 49 of yellow and cyan.

The three superimposed layers 25, 35, and 45 of the diverse subtractive optical filter materials comprising the multi -window structure 11 are combined in a superimposed manner to provide a substantially opaque uniform interstitial webbing that fully surrounds each of the respective filter windows in the screen structure 11 by an opaque uniform peripheral encompassment that is free of indentations. Disposed over these respective dual-layer filter window areas in the screen structure are patterned groupings 57 of compatible green G, blue B, and red R cathodoluminescent phosphor elements, which upon electron excitation produce color emissions that are colormetrically related to respective filter windows 49, 39, and 29 therebeneath.

Portions of the process for fabricating the aforedescribed interstitially defined first 29, second 39 and third 49 dual-layer filter window areas comprising the color cathode ray tube screen structure 11, delineated in FIGS. 1a through 1i of the drawings. I

The process for fabricating the improved multiwindow screen structure is initiated by coating the clean interior surface of the viewing portion of the glass face panel 13 with a uniform layer 15 of a negative photosensitive resist material admixed with an inert protective substance. A negative photosensitive resist composition is a light-activated material that becomes polymerized when exposed to actinic radiation. An example of a negative photosensitive resist composition commonly utilized'in cathode ray tube screen fabrication, is a water-alcohol solution of polyvinyl alcohol sensitized with ammonium dichromate. In the process of the invention, the aforementioned polyvinyl alcohol system alone does not provide the desired definitive protection required in the screen structure'fabrication procedure. Upgrading of this system to provide the necessary protection, to prevent the superposed layers of filter materials from becoming intermixed during fabricating, is effected by admixing therewith an inert protective substance that is thermally and chemically inactive to the temperatures and materials encountered in the process, and one that does not substantially alter the pH of the polyvinyl alcohol system. A suitable material of this type is one such as aluminum silicate, which is also known as Kaolin, zinc oxide, calcium carbonate, and materials related thereto. Preparation of this protective coating material 15, which is also referred to as a stop- I off photoresist, is a two-step formulation procedure.

An initial suspension is first prepared wherein, for example, 40 grams of aluminum silicate and 20 grams of polyvinyl alcohol solids are added to 400 cubic centimeters (cc) of deionized water and ball-milled to provide a complete suspension, which is then filtered to remove any lumps and air bubbles therefrom. Equal volumes of this basic suspension and a monohydric alcohol, such as ethanol or methanol, are admixed and the mixture then sensitized with 3 percent by volume of a 12.5 weight percent of ammonium dichromate solution. As previously mentioned, a uniform coating 15 of this protective material is applied to the face panel as by spraying, flowing, or spinning, whereupon the coated panel is dried.

The apertured patterned mask 17 is positioned in spaced relationship to the coated surface of the panel 13, as shown in FIG. 1a, whereupon the protective photosensitive coating 15 is discretely light exposed by directing actinic radiation X from a specific first exposure position 19 through the multiple apertures in the pattern mask, one of which is shown. The light beam oriented to expose the first window pattern, is sized by the mask aperture 21 whereupon the light impinged window area 31 of the protective coating 15 is photopolymerized by an area of light exposure that are usually slightly larger than the area of the formative aperture 21 in the mask. After exposure, the pattern mask 17 is removed from the proximity of the panel. The light exposed panel coating 15 is then developed, such as by water rinsing, which removes the unexposed photosensitive coating mixture from the panel surface to provide the first polymerized filter pattern window elements 31' which are disposed on the bare glass of the panel 13.

The patterned panel is then overcoated with a uniform primary layer of a heat formable first optical filter material 23, such being illustrated in FIG. lb. An efficient and appropriate class of heat formable optical filter materials, is that represented by the organo-metallic luster compounds, which are commonly known as liquid luster preparations. Such compositions are base metal brganic solutions of metals such as tin, iron, bismuth, titanium and the like, which may contain additions of metallo -organic compounds of precious metals dissolved in organic solvents. The initial'color of such liquid luster preparations usually bear no semblance to the desired optical filter hue resultant from subsequent heat transformation. While luster preparations are available commercially, their formularly compositions are usually considered to be proprietary with the manufacturer of the product. A metallic luster material suitablefor use as the first optical component constituting the primary filter layer 25 in this composite screen structure 11 may be, for example, a cyan-producing luster material which is commercially available from Hanovia Liquid Gold Division, Englehard Industries, Inc., East Newark, N..l. A proprietary lusterthinning composition is added to the luster material to provide a coating thickness evidencing desired optical attenuation and to adjust the viscosity of the liquid luster material to expedite efficient application thereof over the patterned panel surface. It has been found that a coating viscosity in the order of8 to 10 centipoises is appropriate for spin application of the luster material, when rotating the panel in substantially the range of 90 to 150 rpm, whereupon a uniformly applied coating thickness in the order of 2.0 to 3.0 microns is achieved.

Upon drying, the overcoated panel is heated or fired in a controlled oxygen atmosphere at a temperature in the range of 450 to 500 Centigrade, for a time period such as from 2 to 3 hours. This environmentally controlled heating thermally degrades the polymerized first patterned window elements 31' formed of the protective resist mixture. In addition, the heating step transforms and oxidizes the first luster material changing the color thereof to a cyan-hued optical filter material; and further effects adherence of a substantially continuous and transparent glassy primary layer of the. transformed optical filter material wherein the defined first pattern window areas have residuals of the heat degraded protective resist mixture and the associated su perposed filter material loosely retained therein.

The panel is next treated in a manner to remove the loosely retained inert protective and associated filter materials from the first pattern window areas. One removal procedure is in the form of lightly brushing the panel with a non-abrasive means, such as a soft-hair brush. This may be followed by the application of a sweeping of low pressure air, or a water rinse. Another successful removal means is in the form of immersing the screen area in an aqueous solution, such as water and a compatible wetting agent, and then submitting the screen environment to a controlled application of ultrasonic vibrations, after which the screen area is rinsed with water, to completely remove the residuals, and dried. This stage of the partially fabricated screen structure is clearly referenced in FIG. 10 wherein the open first window pattern 31 in the primary filter layer 25 is delineated. The inert component in the resist mixture prevents the first luster material from adhering to the glass surface of the open window pattern areas. The desired thickness of the transformed cyan-huedluster filter material is extremely thin being less than substantially 0.4 microns. It has been found that the thickness of each of the respective optical filter materials comprising the dual-layered optical filter components of I the screen structure shouldeach contribute a light vof a negative photoresist material admixed with an inert substance such as previously disclosed. With reference to FIG. ld, this coating is exposed by directing actinic radiation Y" from a second exposure source through the apertures of the repositioned patterned mask to light polymerize portions of the photosensitive coating mixture 27 in those areas 41' subsequently to be occupied by the'second filter pattern windows. The exposed panel is then developed, as before, by removing the unexposed protective photosensitive mixture therefrom to provide a plurality of second polymerized filter pattern elements 41 superimposed on the first optical filter material 25 in a manner to define the subsequent second filter pattern window areas 41.

In referring to FIG. Ie, the panel is then overcoated with a uniform secondary layer of a heat formable second optical filter material 33, as for example, a second subtractive primary color-producing liquid organometallic luster compound. For instance, this second luster filter material'may be a yellow-producing composition which is also available from Englehard Industries.

The patterned panel 13 is again reheated in the priorly described controlled oxygen atmosphere whereby the polymerized protective resist mixture forming the second 41' patterned window elements, is thermally degraded, but loosely retained with the associated second filter material in the second window areas. The inert protective material contained in the photosensitive resist mixture prevents the second luster material from contaminating the underlying first filter material. This second heating step, additionally transforms and oxidizes the second luster materialchanging the color thereof to a yellow-hued'optical filter material, and further effects adherence of a substantially continuous and transparent glassy secondary layer 35 of the transformed optical filter material to portions of the primary filter layer 25 including deposition in the first filter pattern window areas 31 thereof. The panel is next treated, as before-described, to remove the loosely retained materials from the affected second window areas 41. Thus, the primary filter layer 25 is covered with the secondary filter layer 35 of the second optical filter material having second pattern open filter windows 41 therein, as shown in FIG. 1 f.

At this stage, the panel is again recoated with a uniform layer of the aforementioned protective coating 37 which is formed of the negative photoresist material admixed with an inert substance. Ensuing exposure of the coated panel is consummated by directing actinic radiation, emanating from a third Z exposure position, to

formable third optical filter material, such as another I subtractive primary colorant in the form of a third organo-metallic luster compound, is applied as an overcoating to the patterned panel as shown in FIG. 1h. The luster preparation for this third filter layer may, for example, be a magenta-producing luster, a material also available from Englehard Industries."

The overcoated panel is subjected to a repeat or third heating in a controlled oxygen atmosphere wherein the polymerized third pattern window elements 51 formed of the protective resist mixture are thermally degraded, and whereof the third luster material is transformed, oxidized, and adhered as a substantially continuous and transparent tertiary layer 45 of the third magenta-hued optical filter material to portions of the secondary filter layer 35including deposition in the second filter pattern windows 41 thereof. The tertiary layer evidences defined third filter pattern windows areas 51 therein wherein the degraded protective mixture and associated third filter materials are loosely retained. Removal of these loosely retained materials, as by brushing and rinsing, or by ultrasonic means, produces the third pattern open filter windows 51 in the tertiary layer wherethrough defined areas of the previare evidenced, in superposition, to form the dual-layer third pattern filters 49 as delineated in FIG. li. Material of the tertiary layer being disposed in the second filter pattern windows 41 of the secondary filter layer 35 is superposed on material of the first filter layer 25 therebeneath to form the dual-layer second pattern filters 39. And, the tertiary material superpositionally covering the secondary material disposed in first pattern windows 31 in the primary filter layer 25 form the duallayer first pattern filters 29. The superimposed primary 25, secondary 35, and tertiary 45 filter layers, namely the cyan, yellow, and magenta filtering components, provide in combination a substantially opaque uniform interstitial webbing 55 fully surrounding each of the respective round windows in the multi-windowed screen structure 11. Each filter window is evenly defined by a uniform peripheral encompassment that is free of indentations.

With reference to FIGS. lj and 2, upon completing fabrication of the interstitially defined multi-windowed optical filter screen structure having dual-layer optical filtering components therein as hereinbefore described, the respective green G, red R and blue B cathodoluminescent phosphor elements are suitably disposed as a patterned screen 57 over the appropriate yellow-cyan, yellow-magenta, and magenta-cyan filter windows. Since deposition of the pattern of color emitting phosphor elements is accomplished in a conventional manner by one of the procedures well known in the art, further details of the phosphor screening process will not be considered herein.

It may be considered expedient from the standpoint of phosphor brightness and color emission, to form a multi-windowed screen structure wherein only two of open or free of discrete optical filtering materials, that 6 window area has specific actinic radiation directed to it during each of the primary, secondary, and tertiary filter layer exposures.

'ously disposed first and second optical filter materials -'filter window openings in the opaque interstitial webbing that are smaller than the associated apertures in the patterned mask member subsequently utilized in the operable-tube. In one consideration, the mask apertures initially utilized in forming the filter windows and the defining interstitial webbing, may be subjected to a subsequential chemical etching process to enlarge their sizes thereby effecting a desired dimensional differential between the final sized apertures used in tube operation and theinitially sized apertures utilized in forming the windows in the interstitial webbing. Prior art is replete with a variety of techniques for modifying the sizes of the pattern mask apertures utilized in the forming of or the operation. of specific types of color screen structures. There are several disclosures wherein changing of the aperture sizes is executed by deposition within the aperture openings of peripheral fill-in substances applied, 'as for example, by painting, dipping, electrophoresis, electroplating and vaporization. Such modifieationsof the apertures of the mask member may be utilized as desired in conjunction with the screen structure of the invention.

Thus, there is provided a process for fabricating an improved color. cathode ray tube screen structure that incorporates smoothly defined dual-layered optical filter elements therein which evidence improved selectivity of filtering. The windows which are peripherally defined to befreelof indentations are surrounded by an opaque interstitial webbing of uniform thickness. A screen structure having uniformity of the opaque interstitial encompassment, as provided by this process, effects enhanced absorbency of the ambient light impinging the exterior surface of the viewing panel thereby producing improved contrast of the color display emanating from the screen of the tube.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. In the viewing panel of a color cathode ray tube whereona patterned cathodoluminescent screen formed of green-emitting, blue-emitting, and redemitting phosphor elements is disposed relative to a multiple apertured pattern mask spatially positioned adjacent thereto, an improved process for forming an improved multi-windowed screen structure defined by a webbing of uniform opaque interstices disposed on an interior surface of said panel prior to the fabrication of said patterned phosphor screen thereon, said windows being definitive of dual-layered optical filter components formed of superimposed selected transparent optical filter materials and evidencing peripheral shapings free of indentations similar to those of the respective formative apertures in said pattern mask, said process improvement comprising the steps of:

coating'the interior of said panel with a uniform layer ofa p'rotective coating formed of a negative photosensitive 'resist material admixed with an inert substance, exposing said coated panel by directing actinic radiation emanating from a first exposure position through the apertures in said pattern mask to light polymerize those portions of said photosensitive coating mixture in the areas subsequently occupied by said first filter pattern windows;

developing said light-exposed panel coating by removing the unexposed photosensitive mixture therefrom to provide polymerized first filter pattern window elements on the bare glass of said panel;

overcoating said patterned panel with a uniform liquid primary layer of a heat formable first optical filter material;

heating said overcoated panel in a controlled oxygen atmosphere to thermally degrade said polymerized first window elements formed of said resist mixture and oxidize said first optical filter material and adhere a substantially continuous and transparent primary layer of said first optical filter material to the glass surface of said panel, said primary layer having defined first filter pattern window areas therein wherein said degraded mixture and associated first filter materials are loosely retained;

treating said panel to remove said loosely retained materials from said first filter pattern window areas to provide a primary layer of first optical filter ma terials having a first pattern open filter windows therein;

coating said panel with a uniform layer of said protective coating formed of said negative photoresist material admixed with said inert substance;

exposing said coated panel by directing actinic radiation emanating from a second exposure position through the apertures of said pattern mask to lightpolymerize discrete portions of said photosensitive coating mixture in those areas subsequently occupied by said second filter pattern windows;

developing said light exposed panel coating by removing the unexposed photosensitive mixture therefrom to provide a plurality of second polymerized filter pattern elements superimposed on said first optical filter material in a manner to define the second filter pattern window areas;

overcoating said patterned panel with a uniform liquid secondary layer of a heat formable second optical filter material;

heating said overcoated panel in a controlled oxygen atmosphere to thermally degrade said polymerized second window elements formed of said resist mixture and oxidize and adhere a substantially continuous and transparent secondary layer of said second optical filter material to portions of said primary filter layer including deposition in the first filter pattern windows thereof, said secondary layer having defined second filter pattern window areas therein wherein said degraded mixture and associated second filter materials are loosely retained;

treating said panel to remove said loosely retained materials from said second filter window areas whereupon areas of said primary filter layer are evidenced through said open second filter pattern windows;

coating said panel with a uniform layer of said protective coating formed of said negative photoresist material admixed with said inert substance;

exposing said coated panel by directing actinic radiation emanating from a third exposure position through the apertures in said pattern mask to lightpolymerize discrete portions of said photosensitive coating mixture in those areas subsequently occupied by said third filter pattern windows;

developing said light exposed panel coating by removing the unexposed photosensitive mixture therefrom to provide a plurality of polymerized third filter pattern elements disposed on said secondary filter layer;

overcoating said patterned panel with a uniform liquid tertiary layer of a heat formable third optical filter material;

heating said overcoated panel in a controlled oxygen atmosphere to thermally degrade said polymerized third window elements formed of said resist mixture and oxidize and adhere a substantially continuous and transparent tertiary layer of said third optical filter material to portions of said secondary filter layer including deposition in the second filter pattern windows thereof, said tertiary layer having defined third filter pattern window areas therein wherein said degraded mixture and associated third filter materials are loosely retained; and treating said panel to remove said loosely retained materials from said third filter pattern window areas whereupon areas of said secondary filter layer superposed on said primary filter layer are evidenced through said open third filter pattern windows, areas of said tertiary filter layer superposed on said primary filter layer being evidenced and defined by said second filter pattern windows, areas of said tertiary filters layers superposed on said secondary filter layer being evidenced and defined by said first filter pattern windows; said first, second and third dual-layered filter pattern areas being associated with specific color-emitting phosphor elements to provide enhanced selective optical filtering thereof, the combination of said superimposed filter layers provide an opaque uniformly structured interstitial webbing fully surrounding each of the respective optical filter windows in said screen structure, the uniform peripheral encompassment of each filter window being free of indentations provides an optimized area for display of a respective color emission.

2. A process for fabricating the improved multiwindowed screen structure having dual-layered optical filter components therein according to claim 1 wherein said heat formable optical filter materials are liquid organo-metallic luster compositions.

3. The process for fabricating the improved multiwindowed screen structure having dual-layered optical filter components therein according to claim 1 wherein said first, second, and third optical filter materials are of different compositions, each is representative of a diverse hue being selected from the group of subtractive primary colors consisting of yellow, cyan, and magenta.

4. The process for fabricating the improved multiwindowed screen structure according to claim 1 wherein a window area may be formed and retained as an open window in said screen structure free of filtering materials, said open window being achieved by directing a specific exposure radiation thereto during the exposure steps related to said primary, secondary, and

tertiary layers. 

1. IN THE VIEWING PANEL OF A COLOR CATHODE RAY TUBE WHEREIN A PATTERNED CATHODOLUMINESCENT SCREEN FORMED OF GREENEMITTING, BLUE-EMITTING, AND RED-EMITTING PHOSPHOR ELEMENTS IS DISPOSED RELATIVE TO A MULTIPLE APERTURED PATTERN MASK SPATIALLY POSITIONED ADJACENT THERETO, AN IMPROVED PROCESS FOR FORMING AN IMPROVED MULTI-WINDOWED SCREEN STRUCTURE DEFINED BY A WEBBING OF UNIFORM OPAQUE INTERSTICES DISPOSED ON AN INTERIOR SURFACE OF SAID PANEL PRIOR TO THE FABRICATION OF SAID PATTERNED PHOSPHOR SCREEN THEREON, SAID WINDOWS BEING DEFINITIVE OF DUAL-LAYERED OPTICAL FILTER COMPONENTS FORMED OF SUPERIMPOSED SELECTED TRANSPARENT OPTICAL FILTER MATERIALS AND EVIDENCING PERIPHERAL SHAPINGS FREE OF INDENTATIONS SIMILAR TO THOSE OF THE RESPECTIVE FORMATIVE APERTURES IN SAID PATTERN MASK, SAID PROCESS IMPROVEMENT COMPRISING THE STEPS OF: COATING THE INTERIOR OF SAID PANEL WITH A UNIFORM LAYER OF A PROTECTIVE COATING FORMED OF A NEGATIVE PHOTOSENSITIVE RESIST MATERIAL ADMIXED WITH AN INERT SUBSTANCE; EXPOSING SAID COATED PANEL BY DIRECTING ACTINIC RADIATION EMANATING FROM A FIRST EXPOSURE POSITION THROUGH THE APERTURES IN SAID PATTERN MASK TO LIGHT POLYMERIZE THOSE PORTIONS OF SAID PHOTOSENSITIVE COATING MIXTURE IN THE AREAS SUBSEQUENTLY OCCUPIED BY SAID FIRST FILTER PATTERN WINDOWS; DEVELOPING SAID LIGHT-EXPOSED PANEL COATING BY REMOVING THE UNEXPOSED PHOTOSENSITIVE MIXTURE, THEREFROM TO PROVIDE POLYMERIZED FIRST FILTER PATTERN WINDOW ELEMENTS ON THE BARE GLASS OF SAID PANEL; OVERCOATING SAID PATTERNED PANEL WITH A UNIFORM LIQUID PRIMARY LAYER OF A HEAT FORMABLE FIRST OPTICAL MATERIAL; HEATING SAID OVERCOATED PANEL IN A CONTROLLED OXYGEN ATMOSPHERE TO THERMALLY DEGRADE SAID POLYMERIZED FIRST WINDOW ELEMENTS FORMED OF SAID RESIST MIXTURE AND OXIDIZE SAID FIRST OPTICAL FILTER MATERIAL AND ADHERE A SUBSTANTIALLY CONTINUOUS AND TRANSPARENT PRIMARY LAYER OF SAID FIRST OPTICAL FILTER MATERIAL TO THE GLASS SURFACE OF SAID PANEL; SAID PRIMARY LAYER HAVING DEFINED FIRST FILTER PATTERN WINDOW AREAS THEREIN WHEREIN SAID DEGRADED MIXTURE AND ASSOCIATED FIRST FILTER MATERIALS ARE LOOSELY RETAINED; TREATING SAID PANEL TO REMOVE SAID LOOSELY RETAINED MATERIALS FROM SAID FIRST FILTER PATTERN WINDOW AREAS TO PROVIDE A PRIMARY LAYER OF FIRST OPTICAL FILTER MATERIALS HAVING A FIRST PATTERN OPEN FILTER WINDOWS THEREIN; COATING SAID PANEL WITH A UNIFORM LAYER OF SAID PROTECTIVE COATING FORMED OF SAID NEGATIVE PHOTORESIST MATERIAL ADMIXED WITH SAID INERT SUBSTANCE; EXPOSING SAID COATED PANEL BY DIRECTING ACTINIC RADIATION EMANATING FROM A SECOND EXPOSURE POSITION THROUGH THE APERTURES OF SAID PATTERN MASK TO LIGHT-POLYMERIZE DISCRETE PORTIONS OF SAID PHOTOSENSITIVE COATING MIXTURE IN THOSE AREAS SUBSEQUENTLY OCCUPIED BY SAID SECOND FILTER PATTERN WINDOWS; DEVELOPING SAID LYGHT EXPOSED PANEL COATING BY REMOVING THE UNEXPOSED PHOTOSENSITIVE MIXTURE THEREFROM TO PROVIDE A PLURALITY OF SECOND POLYMERIZED FILTER PATTERN ELEMENTS SUPERIMPOSED ON SAID FIRST OPTICAL FILTER MATERIAL IN A MANNER TO DEFINE THE SECOND FILTER PATTERN WINDOW AREAS; OVERCOATING SAID PATTERNED PANEL WITH A UNIFORM LIQUID SECONDARY LAYER OF A HEAT FORMABLE SECOND OPTICAL FILTER MATERIAL; HEATING SAID OVERCOATED PANEL INA CONTROLLED OXYGEN ATMOSPHERE TO THERMALLY DEGRADE SAID POLYMERIZED SECOND WINDOW ELEMENTS FORMED OF SAID RESIST MIXTURE AND OXIDIZE AND ADHERE A SUBSTANTIALLY CONTINUOUS AND TRANSPARENT SECONDARY LAYER OF SAID SECOND OPTICAL FILTER MATERIAL TO PORTIONS OF SAID PRIMARY FILTER LAYER INCLUDING DEPOSITION IN THE FIRST FILTER PATTERN WINDOWS THEREOF, SAID SECONDARY LAYER HAVING DEFINED SECOND FILTER PATTERN WINDOW AREAS THEREIN WHEREIN SAID DEGRADED MIXTURE AND ASSOCIATED SECOND FILTER MATERIALS ARE LOOSELY RETAINED; TREATING SAID PANEL TO REMOVE SAID LOOSELY RETAINED MATERIALS FROM SAID SECOND FILTER WINDOW AREAS WHEREUPON AREAS OF SAID PRIMARY FILTER LAYER ARE EVIDENCED THROUGH SAID OPEN SECOND FILTE PATTERN WINDOWS; COATING SAID PANEL WITH A UNIFORM LAYER OF SAID PROTECTIVE COATING FORMED OF SAID NEGATIVE PHOTORESIST MATERIAL ADMIXED WITH SAID INERT SUBSTANCE; EXPOSING SAID COATED PANEL BY DIRECTING ACTINIC RADIATION EMANATING FROM A THIRD EXPOSURE POSITION THROUGH THE APERTURES IN SAID PATTERN MASK TO LIGHT-POLYMERIZED DISCRETE PORTIONS OF SAID PHOTOSENSITIVE COATING MIXTURE IN THOSE AREAS SUBSEQUENTLY OCCUPIED BY SAID THIRD FILTER PATTERN WINDOWS; DEVELOPING SAID LIGHT EXPOSED PANEL COATING BY REMOVING THE UNEXPOSED PHOTOSENSITIVE MIXTURE THEREFROM TO PROVIDE A PLURALITY OF POLYMERIZED THIRD FILTER PATTERN ELEMENTS DISPOSED ON SAID SECONDARY FILTER LAYER; OVERCOATING SAID PATTERNED PANEL WITH A UNIFORM LIQUID TERTIARY LAYER OF A HEAT FORMABLE THIRD OPTICAL FILTER MATERIAL; HEATING SAID OVERCOATED PANEL IN A CONTROLLED OXYGEN ATMOSPHERE TO THERMALLY DEGRADE SAID POLYMERIZED THIRD WINDOW ELEMENT FORMED OF SAID RESIST MIXTURE AND OXIDIZE AND ADHERE A SUBSTANTIALLY CONTINUOUS AND TRANSPARENT TERTIATY LAYER OF SAID THIRD OPTICAL FILTER MATERIAL TO PORTIONS OF SAID SECONDARY FILTER LAYER INCLUDING DEPOSITION IN THE SECOND FILTER PATTERN WINDOWS THEREOF, SAID TERTIARY LAYER HAVING DEFINED THIRD FILTER PATTERN WINDOW AREAS THEREIN WHEREIN SAID DEGRADED MIXTURE AND ASSOCIATED THIRD FILTER MATERIALS ARELOOSELY RETAINED; AND TREATING SAID PANEL TO REMOVE SAID LOSSELY RETAINED MATERIALS FROM SAID THIRD FILTER PATTERN WINDOW AREAS WHEREUPON AREAS OF SAID SECONDARY FILTER LAYER SUPERPOSED ON SAID PRIMARY FILTER LAYER ARE EVIDENCED THROUGH SAID OPEN THIRD FILTER PATTERN WINDOWS, AREA OF SAID TERTIRY FILTER LAYER SUPERPOSED ON SAID PRIMARY FILTER LAYER BEING EVIDENCED AND DEFINED BY SAID SECOND FILTER PATTERN WINDOWS, AREAS OF SAID TERTIARY FILTERS LAYERS SUPERPOSED ON SAID SECONDARY FILTER LAYER BEING EVIDENCED AND DEFINED BY SAID FIRST FILTER PATTERN WINDOWS; SAID FIRST, SECOND AND THIRD DUAL-LAYERED FILTER PATTERN AREAS BEING ASSOCIATED WITH SPECIFIC COLOREMITTING PHOSPHOR ELEMENTS TO PROVIDE ENHANCED SELECTIVE OPTICAL FILTERING THEREOF, THE COMBINATION OF SAID SUPERIMPOSED FILTER LAYERS PROVIDE AN OPAQUE UNIFORMLY STRUCTURED INTERSTITIAL WEBBING FULLY SURROUNDING EACH OF THE RESPECTIVE OPTICAL FILTER WINDOWS IN SAID SCREEN STRUCTURE, THE UNIFORM PERIPHERAL ENCOMPASSMENT OF EACH FILTER WINDOW BEING FREE OF INDENTATIONS PROVIDES AN OPTIMIZED AREA FOR DISPLAY OF A RESPECTIVE COLOR EMISSION.
 2. A process for fabricating the improved multi-windowed screen structure having dual-layered optical filter components therein according to claim 1 wherein said heat formable optical filter materials are liquid organo-metallic luster compositions.
 3. The process for fabricating the improved multi-windowed screen structure having dual-layered optical filter components therein according to claim 1 wherein said first, second, and third optical filter materials are of different compositions, each is representative of a diverse hue being selected from the group of subtractive primary colors consisting of yellow, cyan, and magenta.
 4. The process for fabricating the improved multi-windowed screen structure according to claim 1 wherein a window area may be formed and retained as an open window in said screen structure free of filtering materials, said open window being achieved by directing a specific exposure radiation thereto during the exposure steps related to said primary, seconDary, and tertiary layers. 